And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him. (Genesis 4:8)
When Adam and Eve sinned in the garden, God took it upon Himself to slay at least two animals to cover their nakedness (Genesis 3:21). This served as an example of the sacrifice of innocent blood for the covering or “atonement” for sin. “And almost all things are by the law purged with blood; and without shedding of blood is no remission” (Hebrews 9:22). Apparently, the first family continued to offer animal sacrifices as instructed by God and as demonstrated by Abel’s offering. “And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the LORD had respect unto Abel and to his offering” (v. 4).
Cain, however, had his own idea about what to offer the Lord. “Cain brought of the fruit of the ground an offering unto the LORD” (v. 3). Perhaps he rationalized that his offering was worthy because, after all, it had cost him a lot of sweat and back-breaking labor. But this was not what the Lord required. “But unto Cain and to his offering [the LORD] had not respect. And Cain was very wroth, and his countenance fell” (v. 5). Cain’s error was not unlike that of modern religions that attempt to please God by their own schemes and ignore the simple Gospel; “Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified” (Galatians 2:16). Still they persist in inventing their own rules.
“Cain was very wroth, and his countenance fell” (v. 5) when he saw that his offering was unacceptable to God. In his anger, he lashed out at the representation of God’s righteousness, and he murdered his brother. Thus, Abel was martyred for his faith and his righteous acts. In nearly 6000 years, little has changed in that regard. Jesus warned, “And ye shall be hated of all men for my name’s sake: but he that endureth to the end shall be saved” (Matthew 10:22).